UNSPECIFIED (2001) A rare-earth K-edge EXAFS study of rare-earth phosphate glasses, (R2O3)(x)(P2O5)(1-x), x=0.187-0.239, R = La, Nd, Sm, Eu, Gd, Dy, Er. JOURNAL OF PHYSICS-CONDENSED MATTER, 13 (31). pp. 6659-6674. ISSN 0953-8984

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Abstract

A rare-earth K-edge extended x-ray absorption fine structure (EXAFS) study of rare-earth phosphate glasses, (R2O3)(x)(P2O5)(1-x), x = 0.187-0.239, R = La, Nd, Sm, Eu, Gd, Dy, Er, is presented. The structures of these materials were investigated as a function of (a) rare-earth atomic number and (b) temperature, and represent some of the first rare-earth K-edge EXAFS studies on a series of lanthanide-based materials. Results corroborate findings from complementary x-ray and neutron diffraction and magic-angle-spinning (NIAS) NMR experiments, and in addition, they provide a unique insight into the nature of the static disorder of the R-O correlations and of the neighbouring phosphate groups. The effects of multiple-scattering contributions are also discussed within this context. The variable temperature measurements illustrate the exceptionally high level of network rigidity present in these materials. The results are also compared to those obtained from an analogous rare-earth L-III-edge EXAFS (5.483-8.358 keV) study. Results show that the use of the much higher energies of the rare-earth K-edge (38.925-57.486 keV) enable one to avoid the double-electron excitation problems that are associated with the rare-earth L-III-edge EXAFS in the dynamic range of interest. EXAFS fitting and deconvolution simulations show that the large core hole lifetimes associated with the rare-earth K-edge do not significantly detract from the results. The deconvolution. studies also corroborate our findings that the level of fitting to our data cannot realistically be expanded beyond the first R-O shell. This limitation exists despite the exceptional counting statistics of the experiment and the highly uniform samples made possible by the ability to use much thicker samples at the higher energies compared to those used for the (higher absorption) rare-earth L-III-edge EXAFS studies.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics
Journal or Publication Title:	JOURNAL OF PHYSICS-CONDENSED MATTER
Publisher:	IOP PUBLISHING LTD
ISSN:	0953-8984
Date:	6 August 2001
Volume:	13
Number:	31
Number of Pages:	16
Page Range:	pp. 6659-6674
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/11846

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